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Which of the following combinations should be selected for better tuning of an L-C-R circuit used for communication?
A
R = 15 $\Omega$, L = 3.5 H, C = 30 $\mu F$
B
R = 25 $\Omega$, L = 1.5 H, C = 45 $\mu F$
C
R = 20 $\Omega$, L = 1.5 H, C = 35 $\mu F$
D
R = 25 $\Omega$, L = 2.5 H, C = 45 $\mu F$
Explanation
Highest $\frac{1}{R}\sqrt{L/C}$ gives sharpest tuning.
Detailed Solution
For better tuning, the Q-factor must be high: $Q = \frac{\omega_0L}{R} = \frac{1}{\sqrt{LC}}\left(\frac{L}{R}\right) = \frac{1}{R}\sqrt{\frac{L}{C}}$
So R and C should be small and L should be large.
So R and C should be small and L should be large.